Linear semiconductor substrate, and device, device array and module, using the same

ABSTRACT

The linear semiconductor substrate  1  or  2  of the present invention comprises at least one desired thin film  4  formed on a linear substrate  3  having a length ten or more times greater than a width, thickness, or diameter of the linear substrate itself. Adopting semiconductor as the thin film  4  forms a linear semiconductor thin film. The linear semiconductor substrate  1  or  2  of the present invention is produced by utilizing a fiber-drawing technique which is a fabricating technique of optical fibers.

CROSS-REFERENCE

This application is a continuation application of PCT/JP04/013961, filedSep. 24, 2004, which claims priority to U.S. Provisional ApplicationSer. No. 60/505,405, filed Sep. 23, 2003, the entire contents of eachare incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a linear or one-dimensionalsemiconductor substrate as a semiconductor circuit substrate and afabricating method thereof, and a device, a device array, a module, adisplay, a solar cell, a solar cell module using the linearsemiconductor substrate, and a fabricating method thereof.

BACKGROUND ART

Generally, substrates to be typically used, such as semiconductorsubstrates exemplarily made of silicon, gallium arsenide (GaAs), galliumnitride (GaN) and the like, and a glass substrate for display, aretwo-dimensional planar substrates, respectively.

The semiconductor substrates such as made of silicon, GaAs, and the likeare each provided and used in a manner to pull up a molten raw materialby using a seed crystal to thereby fabricate an ingot of single crystal,and to cut it into semiconductor substrates, followed by application ofgrinding and polishing to provide them with mirror surfaces,respectively.

In case of a liquid-crystal oriented TFT (thin film transistor)comprising semiconductor thin films formed on a two-dimensional glasssubstrate, a polycrystalline silicon (hereinafter abbreviated to “p-Si”)or an amorphous silicon (hereinafter abbreviated to “a-Si”) is depositedon a multicomponent two-dimensional (planar) glass substrate by a vacuumprocess such as a plasma CVD (hereinafter abbreviated to “PCVD”). Incase of p-Si, it is achieved to grow a crystal grain into a larger graindiameter, so as to improve a performance of a TFT. In this case, thep-Si is locally heated by laser, in a manner to melt and solidify thep-Si by moving the laser, thereby growing the crystal in a direction ofa horizontal plane of a substrate (this is called “lateral crystalgrowth”). This forms a p-Si recrystallizedly grown in a line along whichthe laser was moved. It is required to repeat this procedure untilachievement of a predetermined width.

Note that upsized two-dimensional substrates have been developed up tonow, so as to decrease a fabricating cost of two-dimensional substrates.Upsized substrates are developed to have a size of 730×920 mm in thefourth generation in the year 2002, and a size of 1,100×1,300 mm in thefifth generation in 2003, and it is thus predicted that the sixthgeneration in 2004 to 2005 will have a size of 1,500×1,800 mm.

Substrates to be each used for a liquid crystal display or a solar cellare provided and used by grinding and polishing a plate glass such asprepared by a float process, and by cutting it into a predeterminedsize. Depending on the usage, such glass is possibly used by cuttingonly, without grinding and polishing.

Meanwhile, concerning a display, there has been filed by SARNOFFCORPORATION located in the United States a Japanese patent application2000-601699 (P2000-601699) disclosing an invention configured tointegrate light emitting devices into a fiber which is rectangle,circular or the like in cross section, and to integrated fibers arebrought them into an array to establish a planar display.

In case of adopting a conventional two-dimensional substrate, upsizing adisplay increases the number of pixels proportionally to the square of ascreen size. As a result, upsizing a screen considerably deteriorates ayield, when a defect occurrence ratio is unchanged. This naturally leadsto an increased fabricating cost per one display, therebyproblematically and considerably increasing a fabricating cost ininverse proportion to the yield. This is because, when even one portionof a screen has a defective device, it is impossible to replace only theportion or an area around it so as to repair the screen.

According to the invention by the SARNOFF CORPORATION, it is possible toreplace only a fiber including a defective device integrated therewithto thereby repair the screen, thereby providing an advantage of aremarkably improved yield. Also disclosed in this patent-relatedreference, is a fabricating method of a fiber including devicesintegrated therewith.

According to the method adopting a fiber substrate (linear substrate)disclosed in the patent-related reference, it becomes possible todownsize a producing apparatus of a display as compared with aconventional method for adopting a two-dimensional substrate. Further,the disclosed method is advantageous in equipment investment andproduction yield, since a size of each surface to be worked can bedownsized by achieving a width of a linear substrate which iscommensurate with a width of each device, thereby allowing a fineworking with a higher precision.

In the method of the patent-related reference, since it is required tofabricate a large number of linear substrates, various processes relatedto the production of linear substrates are to be excellent inproductivity. In this patent-related reference, it is explained in thepatent-related reference that a columnar magnetron plasma source is usedto enable CVD and sputtering deposition at higher rates, respectively.Further, it is to be achieved to provide a plurality of chambers betweena fiber supply reel and a winding reel, thereby continuously orintermittently conducting treatments for cleaning, and for depositing atransparent electrode (ITO, SnO₂, ZnO, or the like), electric conductor(Cu, Al, or the like), OLED (organic EL), electrodes (Mg/Ag, Ca/Al, orthe like), and protective film (oxide film, nitride film, or the like).

Since the transparent electrode (ITO, SnO₂, ZnO, or the like) andelectric conductor (Cu, Al, or the like) are continuously deposited oneach linear substrate in the longitudinal direction thereof, it becomespossible to adopt a pre-worked linear substrate which results in atreatment process excluding the corresponding procedures. As afabricating method of the pre-worked fiber, it is disclosed to obtainthe same by coating an ITO layer, electric conductor, or another desiredlayer onto a quartz fiber just after drawing it.

There will be now explained a related art of a solar cell. Solar cellsare each capable of directly converting a substantially exhaustlesssolar energy into an electrical energy, thereby serving as a cleanenergy. Based thereon, solar cells each acts as one of the energies,which never cause environmental problems, and to which an attention isdirected as an alternative of thermal power generation using a fossilfuel. Only, due to an increased fabricating cost of solar cells, it is apresent state in Japan that an electricity rate based on powergeneration by solar cells is about 70 yen/kWh (2003) which is aboutthree times as expensive as an electricity rate of 25 yen/kWh of themains-power.

Presently, there are mainly utilized solar cells each adopting a singlecrystal silicon substrate or polycrystalline silicon substrate which isexcellent in conversion efficiency. In this case, it is typical to adopta P type substrate, and to dope phosphorus (P) into a surface of thesubstrate to thereby bring the surface into an N type semiconductor,thereby forming a PN junction in a thickness direction of the substrate.Further, the substrate is formed with electrodes at an obverse surfaceand a reverse surface of the substrate, respectively, and the surfacesof the substrate is coated by a protective film(s) of silicon dioxide(SiO₂) or silicon nitride (Si₃N₄), thereby establishing a solar cell.Further, there is provided a solar cell module by integrating aplurality of the solar cells into a panel, and there is further provideda solar cell array by integrating a plurality of the modules. This solarcell array is combined with a discharge/charge controller, battery,inverter, or the like, thereby establishing a solar cell system.

Meanwhile, there has been disclosed a technique concerning a solar cellwithout using silicon substrates. This is to use a multicomponent glasssubstrate (blue plate glass or white plate glass) as a substrate. Theglass substrate is formed thereon with a film of SiO₂ at a relativelylow temperature of about 300° C. by sputtering, vapor deposition, CVD orthe like, and there is further formed thereon a transparentelectroconductive film of ITO (InSnO₂), SnO₂, ZnO, or the like bysputtering. Further deposited on the transparent electroconductive filmis amorphous silicon (hereinafter abbreviated to “a-Si”) by a PCVDmethod. Devices are each provided in a structure of PIN diode comprisingthree layers of P type, I type, and N type, for example. Furtherdeposited on the a-Si is a reverse surface electrode by vapordeposition, sputtering, or the like. Since the a-Si can be deposited ata low temperature, it is possible to form it into a transparent film. Inthe solar cell as described above, there is used a substrate having asize of 1 m² and a thickness of 4 mm. As a result, its weight becomes asheavy as about 9 kg.

In addition to the above description, there have been also investigatedbinary compound semiconductors such as GaAs, InP, CdS, CdTe or the like,or ternary compound semiconductors such as CuInSe₂. Further, there hasbeen also developed a pigment-impregnated solar cell comprising a porousTiO₂ impregnated with pigment. There has been further developed a solarcell utilizing organic semiconductor. Also in these solar cells,semiconductor substrates or glass substrates are used.

Further, described in U.S. Pat. No. 5,437,736 (Semiconductor Fiber SolarCells and Modules) is an invention configured to provide solar cellseach obtained by coating an electroconductive layer such as molybdenum(Mo) onto a curved face of an optical fiber and by partially formingfirst and second semiconductor layers in arched shapes on the opticalfiber, so as to array the solar cells in a planar shape to thereby forma solar cell module. In the described invention, it is shown to depositMo by a fiber-drawing process in FIGS. 14, 17 of the U.S. Patent.Deposited on the fiber wound on a spool are two semiconductor films in aseparate process, followed by deposition of a transparent electrode,thereby establishing a solar cell.

-   Patent-related reference 1: Japanese Patent Application No.    2000-601699-   Patent-related reference 2: U.S. Pat. No. 5,437,736

DISCLOSURE OF INVENTION Problem to be Solved by the Invention

While silicon single crystal substrates are each about 0.3 mm inthickness in case of φ4″ and about 0.8 mm in case of φ12″, thoseportions functioning as devices are on the order of several hundreds nmto 1 μm in depth from a surface of a substrate in case of a MOSFET(metal oxide semiconductor field effect transistor) mainly used in LSIand VLSI, for example. Further, thermally-oxidized films for gates areeach 100 nm or less in thickness. Thus, in case of silicon singlecrystal substrates, those portions having functions as devices are eachabout 0.1 to 0.3% in depth from the surface of the substrate, so thatmost of the substrate merely functions as a simple structural body.

In a fabricating process of an Si substrate, grown from a silicon meltheated to a temperature above its melting point, is a crystal to a tipend of a seed crystal, and the crystal is grown by pulling up, therebyfabricating an ingot. Thereafter, the ingot is ground into a cylindricalshape, and cut into substrates, which are each ground and polished atits surface, thereby fabricating wafers, respectively. During theseprocesses, there is removed about ½ to ⅓ of the weight of the pulled upingot. Thereafter, 20% to 30% of the resultant weight is furtherremoved, in a process for bringing each wafer formed with devices intochips. Thus, the effectively utilized ratio of silicon is about 50% at astage of the final chip process as compared with the initial stage, sothat high purity silicon can not be regarded as being effectivelyutilized.

Meanwhile, in case of a liquid-crystal oriented TFT comprisingsemiconductor thin films formed on a two-dimensional glass substrate, itis achieved to grow a p-Si crystal grain by laser. However,two-dimensional substrates to be used are each typically made ofmulticomponent glass having a melting point (about 600° C.) which islower than that of Si because only two-dimensional substrates made ofinexpensive materials are usable from a standpoint of cost, resulting inthat each substrate is allowed to be heated only locally. As such, ithas been required to form p-Si and a-Si by PCVD or sputtering which isslow in deposition rate, and to grow a crystal grain by laser anneal. Incase of achieving recrystallization by laser anneal, it is required towiden laser beam into a sheet shape, thereby problematically requiringusage of YAG or excimer laser which has a larger power and is thusexpensive. Further, p-Si including a lot of crystal grains acting asnuclei exists around the portion melted by the laser sheet or beam,thereby problematically and essentially making it difficult to obtain alarger crystal grain boundary.

To attain two-dimensional substrates at a decreased cost, it is nowpromoted to provide upsized substrates. However, it is required to use alow temperature process due to restriction by substrates, therebyrequiring to use an expensive vacuum apparatus, resulting in aconsiderably increased equipment cost due to the upsizing. Meanwhile, inthe conventional fabricating methods of two-dimensional substrates, itis required to improve accuracies of various processes simultaneouslywith increased substrate sizes in a manner to necessitate large-sizedproducing apparatuses with higher accuracies, thereby requiring anenormous equipment investment due to the increased substrate sizes.

In the invention of the patent-related reference 1 related to a display,there is adopted a reel-to-reel scheme, thereby causing a problem of alower productivity even by the used expensive vacuum apparatus. Further,in case of adopting glass fibers, the glass fibers are each provided ina structure to be contacted with a guide roll and a mask, and it isfurther required to apply a tension to the fiber so as to straightlystretch it. In turn, when a fine crack is caused in a fiber due tocontact thereof with a guide roll or the like, the fiber may be brokenat the crack. Once the breakage is caused, the associated vacuumapparatus is required to be stopped, thereby not only considerablydeteriorating an operation rate but also exposing the fiber to theatmosphere, in a manner to cause adsorption of or reaction with theatmosphere by the fiber, thereby possibly failing to conduct a normalprocess.

Further, in the invention of the patent-related reference 1, although itis described to continuously produce a transparent electroconductivefilm such as ITO or the like and an electroconductive film such as metalor the like in the course of the fiber-drawing process for producing thefibers by describing that “a quartz fiber is coated with an ITO layer,an electroconductive layer, or another suitable layer, just after thefiber is stretched during production, for example”, the fabricatingmethod therefor is never disclosed. Further, no description is found interms of semiconductor substrates and the like.

In turn, concerning solar cells, although it is required to decrease afabricating cost thereof to decrease an electricity rate, this isextremely difficult because the raw material cost (substrate cost) isextremely high in a method adopting silicon substrates. On the otherhand, in the method for adopting glass substrates, it is beinginvestigated to decrease a fabricating cost by upsizing a substrate andby improving a throughput. In the present state, although solar cellsadopting a-Si are most promising for a decreased cost, deposition ofa-Si is to be conducted at a low temperature such that improvement ofdeposition rate is difficult, thereby problematically failing to attainan increased film thickness. Further, a-Si has an absorption wavelengthband of 0.8 μm or shorter which is narrower than that of 1.1 μm orshorter of a polycrystalline silicon, thereby problematically lower aconversion efficiency of a solar cell using a-Si. Moreover, even in caseof achievement of an upsized glass substrate for a decreased cost, it isalso required to provide large-sized producing apparatuses as describedabove, thereby problematically and considerably increasing an equipmentcost. Furthermore, upsized substrates lead to increased weights, therebycausing a secondary problem of increased transference cost, installationcost, and the like.

In the patent-related reference 2, although there are disclosed opticalfibers, and electroconductive films to be coated onto surfaces of thefibers, no disclosure is found about a fabricating method thereof.Further, the process for depositing semiconductors is separate from thefiber-drawing process and the deposition method is a vapor depositionmethod, thereby causing a problem that the deposition rate is slow tothereby lower the productivity, and crystal grain diameters are alsomade small to thereby only obtain semiconductor films which are not soexcellent in crystallinity.

Means for Solving the Problem

To solve the above problems, the present invention provides thefollowing constitutions as means for solving the problems.

Namely, the present invention provides a first configuration residing ina linear substrate characterized in that the linear substrate comprisesa line-shaped backing having a length more than ten times greater than awidth, thickness, or diameter of the backing (hereinafter called “linearsubstrate”), and at least one layer of desired thin film formed on thelinear substrate.

The present invention provides a second configuration residing in thelinear semiconductor substrate, characterized in that the thin film is asemiconductor thin film.

The present invention provides a third configuration residing in thelinear semiconductor substrate, characterized in that there is used ahigh melting point material made of ceramics such as quartz glass,multicomponent glass, sapphire, alumina, carbon, silicon carbide, andthe like as the linear substrate.

The present invention provides a fourth configuration residing in thelinear semiconductor substrate, characterized in that the linearsemiconductor substrate is in a rectangular or polygonal cross section.

The present invention provides a fifth configuration residing in thelinear semiconductor substrate, characterized in that the ratio(=(R/[length of straight portion])×100) between each R at a corner and alength of a straight portion of the cross section is 10% to 50%.

The present invention provides a sixth configuration residing in thelinear semiconductor substrate, characterized in that the semiconductorthin film has a surface deposited with SiO₂ or Si₃N₄.

The present invention provides a seventh configuration residing in thelinear semiconductor substrate, characterized in that the SiO₂ comprisesa thermally-oxidized film or is formed by a thermal CVD method.

The present invention provides an eighth configuration residing in thelinear semiconductor substrate, characterized in that the semiconductorthin film has a thickness between 10 nm inclusive and 1 μm inclusive.

The present invention provides a ninth configuration residing in thelinear semiconductor substrate, characterized in that the semiconductorthin film has a grain boundary between 10 μm inclusive and 1,000 μminclusive.

The present invention provides a tenth configuration residing in thelinear semiconductor substrate, characterized in that the semiconductorthin film, or an insulating film deposited on the semiconductor thinfilm, is coated thereon with a resist material, UV curable resin,electron beam cross-linking resin, or the like.

The present invention provides an 11th configuration residing in thelinear semiconductor substrate, characterized in that the linearsemiconductor substrate is covered by the semiconductor thin film at aside surface (surface in the longitudinal direction) of the former.

The present invention provides a 12th configuration residing in asemiconductor device and a module, the semiconductor device beingprovided as a chip formed with electronic elements such as diode, IC,LSI, or the like, optical elements such as LD, PD, LED, or the like,solely, plurally, or combinedly, and the module including it/themincorporated thereinto, characterized in that the linear substrate isused as a substrate for fabricating the device.

The present invention provides a 13th configuration residing in asemiconductor steric device (hereinafter called “three-dimensionaldevice”) and a module using the three-dimensional device, characterizedin that the three-dimensional device includes, as the linear substratetherefor, the linear substrate having a substantially rectangular orsubstantially polygonal cross section, and the linear substrate has aplurality of surfaces three-dimensionally formed with devices, circuits,and/or wirings, respectively.

The present invention provides a 14th configuration residing in thethree-dimensional device and the module using the three-dimensionaldevice, characterized in that one or two of the surfaces of thethree-dimensional device is/are used as an electrical contactportion(s).

The present invention provides a 15th configuration residing in thethree-dimensional device and the module using the three-dimensionaldevice, characterized in that at least device portions are formed on thesame surface.

The present invention provides a 16th configuration residing in thethree-dimensional device and the module using the three-dimensionaldevice, characterized in that the linear substrate is formed with apolycrystalline semiconductor film having a grain boundary size of 10 μmto 1,000 μm.

The present invention provides a 17th configuration residing in asemiconductor device array characterized in that the semiconductordevices are formed in the longitudinal direction of the linear substrateat predetermined pitches.

The present invention provides an 18th configuration residing in thesemiconductor device and the semiconductor device array, characterizedin that the linear semiconductor substrate has a plurality of surfacesformed with the same or different ones of the semiconductor devices orthe semiconductor device arrays, respectively.

The present invention provides a 19th configuration residing in a linearelectroconductive substrate characterized in that at least one of thesemiconductor thin films deposited on the linear semiconductor substrateis an electroconductive film, and

that another of the semiconductor thin films is a liquid resin obtainedby coating a resin, or a resin obtained by coating and hardening aresin.

The present invention provides a 20th configuration residing in thelinear electroconductive substrate, characterized in that theelectroconductive film is the semiconductor thin film which issubstantially transparent in a visible range, and which comprises indiumtin oxide (ITO), tin oxide (SnO₂) or zinc oxide (ZnO).

The present invention provides a 21st configuration residing in thelinear electroconductive substrate, characterized in that the resin tobe coated is: a resist; a UV curable resin; silicone; oils such asfluorine oil, mineral oil, and the like; greases of the oils; and thelike.

The present invention provides a 22nd configuration residing in thelinear substrate, characterized in that the thin film formed on thefiber comprises at least one kind of metal or oxide film, or combinationthereof.

The present invention provides a 23rd configuration residing in thelinear substrate, characterized in that the metal or oxide film has aspecific resistance at least included in a range of 10⁻⁴ Ωcm to 10⁻⁸Ωcm.

The present invention provides a 24th configuration residing in thelinear substrate, characterized in that the linear substrate includes alinear substrate provided by drawing out a metal through a die or byrolling the metal into a linear material.

The present invention provides a 25th configuration residing in thelinear substrate, characterized in that the linear substrate is formedwith one or more layers of oxide films or metal films.

The present invention provides a 26th configuration residing in, in afiber-drawing method comprising the steps of:

melting a glass parent material worked into a desired shape within aheating furnace and spinning the material, or melting a glass rawmaterial within a heated crucible and spinning the material, to therebyproduce a fiber;

withdrawing the spun and produced fiber by a withdrawer whilecontrolling a withdrawing speed of the fiber, or a feeding speed of theparent material, or both, so that the spun and produced fiber has aconstant outer diameter; and

winding up the fiber by a winder;

a linear substrate fabricating method for producing the linearsubstrate, characterized in that the linear substrate fabricating methodcomprises the step of:

forming the or each thin film on the fiber during fiber-drawing, therebyproducing the linear substrate.

The present invention provides a 27th configuration residing in thelinear semiconductor substrate fabricating method, characterized in thatthe or each thin film formed on the fiber is the semiconductor thinfilm.

The present invention provides a 28th configuration residing in thelinear semiconductor substrate fabricating method, characterized in thatthe semiconductor thin film is formed before the fiber is contacted witha solid matter.

The present invention provides a 29th configuration residing in thelinear semiconductor substrate fabricating method, characterized in thatthe fiber is formed with at least a part of the or each thin filmbetween the heating furnace or the crucible and the withdrawer.

The present invention provides a 30th configuration residing in thelinear semiconductor substrate fabricating method, characterized in thatthe semiconductor thin film is formed by a CVD method utilizing heat,electromagnetic induction, light, or the like.

The present invention provides a 31st configuration residing in thelinear semiconductor substrate fabricating method, characterized in thatthe semiconductor thin film is formed by using a thermal CVD methodwhich utilizes a heat of the drawn fiber.

The present invention provides a 32nd configuration residing in thelinear semiconductor substrate fabricating method, characterized in thatformation of the semiconductor thin film is conducted in a reactionfurnace which is integral with the heating furnace or in a reactionfurnace which is separate from the heating furnace.

The present invention provides a 33rd configuration residing in thelinear semiconductor substrate fabricating method, characterized in thatthe semiconductor thin film is formed in a state between a substantiallyatmospheric pressure state and a pressurized state.

The present invention provides a 34th configuration residing in thelinear semiconductor substrate fabricating method, characterized in thatthe drawn fiber is coated with a resin or liquid matter includingdeposition particles followed by firing or melting by a heating furnace,to thereby form the desired semiconductor thin film.

The present invention provides a 35th configuration residing in thelinear semiconductor substrate fabricating method, characterized in thatthe semiconductor thin film is formed by coating a molten liquid ontothe fiber, the molten liquid being obtained by heating a material to bedeposited, to a temperature at or higher than a melting point of thematerial.

The present invention provides a 36th configuration residing in thelinear semiconductor substrate fabricating method, characterized in thatthere is provided a step for growing a grain diameter of a depositedlyformed crystal grain by providing the crystal grain with an energy suchas light, heat, electromagnetic induction, or the like, before the fiberdeposited with the film is withdrawn to the withdrawer.

The present invention provides a 37th configuration residing in thelinear semiconductor substrate fabricating method, characterized in thatthere is provided a step for irradiating laser light to thereby conductrecrystallization, after fiber-drawing.

The present invention provides a 38th configuration residing in thelinear semiconductor substrate fabricating method, characterized in thatin the step for growing the crystal grain, the deposited semiconductorthin film is passed through an ambience including a temperaturedistribution with a temperature lowered in a fiber-drawing directionfrom a temperature at or higher than a melting point of the depositedsemiconductor thin film.

The present invention provides a 39th configuration residing in thelinear semiconductor substrate fabricating method, characterized in thatthere is conducted a procedure to enlarge the crystal grain of theformed semiconductor thin film, during the fiber-drawing step or duringanother step, to thereby bring the grain diameter of the crystal grainto φ40 microns or more.

The present invention provides a 40th configuration residing in thelinear semiconductor substrate fabricating method, characterized in thatthere is formed an SiO₂ film or Si₃N₄ film as a second layer.

The present invention provides a 41st configuration residing in thelinear semiconductor substrate fabricating method, characterized in thatsecond layer and third layer are provided by a combination of an SiO₂film and an Si₃N₄ film.

The present invention provides a 42nd configuration residing in, in afiber-drawing method comprising the steps of:

melting a glass parent material worked into a desired shape within aheating furnace and spinning the material, or melting a glass rawmaterial within a heated crucible and spinning the material, to therebyproduce a fiber;

withdrawing the spun and produced fiber by a withdrawer whilecontrolling a withdrawing speed of the fiber, or a feeding speed of theparent material, or both, so that the spun fiber has a constant outerdiameter; and

winding up the fiber by a winder;

a linear substrate fabricating method for producing the linearsubstrate, characterized in that the linear substrate fabricating methodcomprises the step of:

reducing a surface of the spun fiber to thereby form the semiconductorthin film made of silicon.

The present invention provides a 43rd configuration residing in thelinear semiconductor substrate fabricating method, characterized in thatthere is added a step for growing a grain of the silicon forming thesemiconductor thin film.

The present invention provides a 44th configuration residing in thelinear semiconductor substrate fabricating method, characterized in thatthe step for growing the grain of the silicon comprises two or moresteps including a nucleus generation step, and a crystal growth step.

The present invention provides a 45th configuration residing in thelinear semiconductor substrate fabricating method, characterized in thatthe heating temperature is set within a range of 400° C. to 1,000° C. inthe nucleus generation step, and within a range of 1,000° C. to 1,500°C. in the crystal growth step.

The present invention provides a 46th configuration residing in thelinear semiconductor substrate fabricating method, characterized in thatthe step is configured to change a deposition rate in terms of aposition in a longitudinal direction.

The present invention provides a 47th configuration residing in thelinear semiconductor substrate fabricating method, characterized in thatthere is provided a coating step before the fiber is withdrawn by thewithdrawer.

The present invention provides a 48th configuration residing in a methodof fabricating a device from a semiconductor element or from a compositeelement including combined semiconductor elements, characterized in thatthe method comprises the steps of:

integrating the linear semiconductor substrate into a flat plane shape,cylindrical shape, or the like to thereby obtain an integratedsubstrate; and

conducting a whole or part of various procedures for fabricating thedevice, including cleaning, etching, depositing, patterning procedures,and the like.

The present invention provides a 49th configuration residing in themethod for fabricating a device, characterized in that the step offorming the integrated substrate is constituted of:

means for drawing out the coated linear semiconductor substrate wound ona bobbin, at a constant tension;

means for fixing the linear semiconductor substrate onto anintegrated-substrate holder;

integrated-substrate holder moving means for moving theintegrated-substrate holder to thereby arrange the linear semiconductorsubstrate at intervals of predetermined spacings; and

means for cutting the linear semiconductor substrate.

The present invention provides a 50th configuration residing in, in afiber-drawing method comprising the steps of:

melting a glass parent material in a heating furnace and spinning thematerial, or melting a glass raw material within a heated crucible andspinning the material, to thereby produce a fiber;

withdrawing the spun fiber by a withdrawer while controlling in a mannerthat the fiber has a constant outer shape; and

winding up the fiber by a winder;

a linear solar cell fabricating method, characterized in that the linearsolar cell fabricating method comprises the step of:

forming a part or whole of an internal electrode and of semiconductorlayers to be matured into a solar cell, between the heating furnace orthe crucible and the withdrawer.

The present invention provides a 51st configuration residing in thelinear solar cell fabricating method, characterized in that there isprovided a step for forming an intermediate layer between the fiber andthe internal electrode.

The present invention provides a 52nd configuration residing in thelinear solar cell fabricating method, characterized in that thesemiconductor layers are formed by supplying semiconductor raw materialgases into a heating furnace for semiconductor film deposition.

The present invention provides a 53rd configuration residing in thelinear solar cell fabricating method, characterized in that at least apart of the semiconductor layers is deposited by coating semiconductorparticles dispersed in a solvent onto the running fiber, followed bydrying and heating.

The present invention provides a 54th configuration residing in a fibertype solar cell fabricating method comprising the steps of:

forming semiconductor layers to be matured into a solar cell on a linearsubstrate (fiber, wire);

appropriately conducting procedures of electrode formation, elementseparation, and inter-element wiring; and

forming one or more elements in a longitudinal direction of the linearsubstrate, thereby establishing a solar cell.

The present invention provides a 55th configuration residing in a fibertype solar cell fabricating method comprising the steps of:

adopting a linear substrate comprising a fiber-shaped glass backingformed with an internal electrode, and/or an N type or P typesemiconductor layer to be included in a solar cell; and

conducting a process to bring the linear substrate into a solar cell, byachieving at least procedures: to deposit a semiconductor having apolarity opposite to that of the linear substrate, or to form asemiconductor having a relatively high resistance and deposit or dope asemiconductor having a polarity opposite to that of the linearsubstrate, thereby forming elements; to separate the elements from eachother; and to form electrodes between the elements, respectively.

The present invention provides a 56th configuration residing in a fibertype solar cell fabricating method characterized in that the methodcomprises the step of:

adopting a linear substrate comprising a linear substrate formed with apart or whole of electrodes, semiconductor films, and the likeconstituting solar cell elements to thereby implement solar cellprocedures, to fabricate a linear solar cell.

The present invention provides a 57th configuration residing in a fibertype solar cell fabricating method comprising the steps of:

fabricating a linear substrate (fiber, wire) or linear substrate;

cutting the linear substrate or linear substrate into predeterminedlengths, and integrating them with each other into an integratedsubstrate; and

conducting required procedures for fabricating solar cell elements onthe integrated substrate, thereby fabricating a solar cell.

Effect of the Invention

According to the present invention, there is introduced a concept of alinear substrate into a field of semiconductor substrate for the firsttime, it becomes possible to decrease a thickness of a semiconductorlayer down to a required minimum, to thereby drastically decrease a rawmaterial cost of the semiconductor substrate. Further, high meltingpoint backings such as quartz glass or the like are each used as thelinear substrate to thereby enable usage of a thermal process in anordinary pressure state or pressurized state, to realize fabricating oflinear semiconductor substrates simultaneously in a high speed mannerand a mass-production manner, thereby allowing for a decreasedfabricating cost. Furthermore, the linear semiconductor substrates areeach made to have a cross section in a rectangular shape, polygonalshape or the like, thereby enabling a plurality of faces of each linearsemiconductor substrate to be sterically formed with devices, circuits,and/or wirings, respectively, to thereby remarkably improve anintegration ratio of a chip (steric chip, or 3-dimensional chip).

Moreover, the present invention is configured to adopt a procedure tofabricate devices after segmenting the linear substrate, to therebyenable production of the devices at a higher throughput in a manner toremarkably downsize segmented substrates (substrate size of ⅕ to 1/20),thereby allowing for a drastically decreased equipment cost.

Furthermore, according to present invention, the linear semiconductorsubstrate is applied to a solar cell to thereby enable crystal graindiameters of silicon to be made greater than the conventional, and thereis realized multiplex reflection of light within the linearsemiconductor substrate to thereby allow for realization of a powergeneration efficiency of about 20% at the maximum. Moreover, adoption ofthe linear semiconductor substrate enables a weight of solar cell to beremarkably decreased (about 1/10).

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a cross-sectional view of linear substrates according to afirst embodiment of the present invention.

FIG. 2 is a cross-sectional view of linear semiconductor substratesaccording to a second embodiment of the present invention.

FIG. 3 is a cross-sectional view of linear semiconductor substratesaccording to a third embodiment of the present invention.

FIG. 4 is a view of a semiconductor device and a device array adopting alinear semiconductor substrate according to a fourth embodiment of thepresent invention.

FIG. 5 is a view of a device or a device array including semiconductordevices and the like formed on a plurality of surfaces of a linearsubstrate of the present invention. FIG. 5( a) shows an example of alinear substrate having a hexagonal cross section, and FIG. 5( b) showsanother example of a linear substrate having an octagonal cross section.

FIG. 6 is a view of an outline of a linear solar cell according to afifth embodiment of the present invention. FIG. 6( a) shows a structureof the linear solar cell of the fifth embodiment. FIG. 6( b) is across-sectional view of the linear solar cell.

FIG. 7 is a view of an outline of a linear solar cell according to asixth embodiment of the present invention. FIG. 7( a) shows a structureof the linear solar cell of the sixth embodiment. FIG. 7( b) is across-sectional view of the linear solar cell.

FIG. 8 is a view of a structure of a solar cell module of the presentinvention.

FIG. 9 is a schematic view of a solar cell system adopting linearsubstrates according to a seventh embodiment of the present invention.FIG. 9( a) is a view of an example of a solar cell module, and FIG. 9(b) is a constitutional view of the solar cell system where the solarcell module is used as an AC electric-power source.

FIG. 10 is a constitutional view of a solar cell in a bamboo blind shapeas an embodiment of a solar cell of the present invention.

FIG. 11 is an explanatory view of a fabricating method of a linearsemiconductor substrate of the present invention.

FIG. 12 is an explanatory view of a linear semiconductor substrate ofthe present invention, including mutually separated fiber-drawingfurnace and reaction furnace.

FIG. 13 is an explanatory view of another fabricating method of a linearsemiconductor substrate of the present invention.

FIG. 14 is an explanatory view of a fabricating method of a linearsemiconductor substrate of the present invention, for forming two layersof P type polycrystalline silicon and N type polycrystalline siliconcooperatively constituting a solar cell.

FIG. 15 is an explanatory view of still another fabricating method of alinear semiconductor substrate of the present invention.

FIG. 16 is an explanatory view of a fabricating method of atwo-dimensional or curve surfaced module adopting the linear substrateof the present invention.

FIG. 17 is an explanatory view of another fabricating method of atwo-dimensional or curve surfaced module adopting the linear substrateof the present invention.

FIG. 18 is an explanatory view of a supply method of a raw material gasinto a reaction furnace.

FIG. 19 is an explanatory view of another supply method of a rawmaterial gas into a reaction furnace.

FIG. 20 is an explanatory view of details of a gas injection portion anda gas suction portion of the reaction furnace.

EXPLANATION OF REFERENCE NUMERALS

-   -   1, 2, 5, 6, 8, 9 . . . linear semiconductor substrate    -   3, 22, 41, 51 . . . quartz glass (fiber)    -   4, 10, 11, 23 . . . polycrystalline silicon    -   7 . . . thin film    -   21 . . . semiconductor device    -   24 . . . gate insulating film    -   25 . . . inter-layer insulating film    -   26 . . . electric current supplying source    -   27 . . . signal line    -   31 . . . silicon device    -   32, 58 . . . insulating film    -   33 . . . protective film    -   34, 45, 55 . . . electrode    -   35, 47, 57 . . . wiring    -   36 . . . mount board    -   37 . . . wiring of mount    -   42, 53 . . . P type polycrystalline silicon    -   43, 52 . . . P+ type polycrystalline silicon    -   44, 54 . . . N+ type polycrystalline silicon    -   46, 56 . . . solar cell element    -   61, 72, 79 . . . linear solar cell    -   62, 73 . . . reflective plate    -   63 . . . anti-reflection film    -   71 . . . solar cell module    -   74 . . . discharge/charge controller    -   75 . . . inverter    -   76 . . . battery    -   77 . . . load    -   78 . . . solar cell    -   101 . . . preform    -   102 . . . first heater    -   103 . . . second heater    -   104 . . . third heater    -   105 . . . fourth heater    -   106 . . . reaction furnace core pipe    -   107, 108 . . . exhaust port    -   109 . . . cooling apparatus    -   110 . . . resist coating portion    -   111 . . . resist hardening portion    -   112 . . . capstan    -   113 . . . double spooler    -   121 . . . fiber-drawing furnace    -   122 . . . reaction furnace    -   123 . . . coupling tube    -   131, 132, 133 . . . supply port    -   141 . . . coating apparatus    -   142 . . . melting/solidifying portion    -   151 . . . linear substrate fabricating process    -   152 . . . segmenting process    -   153, 162 . . . device fabrication process    -   154, 163 . . . modularizing process    -   155 . . . roller substrate    -   161 . . . linear substrate/backing fabricating process    -   164 . . . linear substrate supply bobbin    -   165 . . . coating removal step    -   166 . . . semiconductor deposition step    -   167 . . . doping step    -   168 . . . element separation step    -   169 . . . electrode formation step    -   170 . . . cutting step

BEST MODE FOR CARRYING OUT THE INVENTION

There will be described preferred embodiments of the present invention,with reference to the drawings.

First Embodiment

There will be firstly explained a linear substrate according to a firstembodiment, with reference to the drawings. FIG. 1 is a cross-sectionalview of linear substrates according to the first embodiment. The linearsubstrates of the present invention each comprises at least one desiredthin film formed on or around a linear substrate having a length ten ormore times greater than a width, thickness, or diameter of the linearsubstrate itself. Although FIG. 1 shows only cross sections of thelinear substrates, the linear substrates of the present invention eachhave a sufficient length more than ten times greater than a width,thickness, or diameter of the illustrated cross section.

In the first embodiment, there will be described a linear semiconductorsubstrate to be used as a semiconductor substrate, among linearsubstrates. FIG. 1 shows linear semiconductor substrates 1 and 2 eachcomprising a polycrystalline silicon (p-Si) 4 as a semiconductor thinfilm deposited on an associated quartz glass backing 3. Further, thelinear semiconductor substrates 1 and 2 are examples having rectangleand circular cross-sectional shapes, respectively.

Cross-sectional shapes of the linear semiconductor substrates possiblyinclude: a circular shape; rectangular or polygonal shapes, such as asquare or rectangle, having R-ed (radiused) corners; a shape provided bycombining a semicircle and a rectangle; a shape provided by combining acurved face and a rectangle; and the like. In case of the rectangular orpolygonal shapes having R-ed (radiused) corners, it is desirable thatthe ratio (=R/[length of straight portion]×100) between each R at acorner and a length of a straight portion is 10% to 50%. It is alsopossible to provide a cross section having a center hole. In case ofrectangle, polygonal shapes and the like, it is possible to form adevice, circuit, and the like at each face, thereby enabling improvementof an integration ratio as compared with a planar substrate.

The linear semiconductor substrates of the present invention can be eachused as an alternative of an expensive silicon wafer serving as aconventional two-dimensional semiconductor substrate. In this case, eachpolycrystalline silicon 4 is to be desirably deposited in a range of 10nm (desirably 50 nm or more) to 1,000 nm, and crystal grain diametersare desirably between 10 μm inclusive and 1,000 μm inclusive.

In case of forming a device, circuit, or the like within one grainboundary, there is required a grain boundary size of 10 μm at theminimum in consideration of a device size and an alignment accuracy,though such required grain boundary sizes depend on types of devices.Adopting a substrate having a grain boundary size larger than a devicesize enables formation of a device, circuit, or the like within thegrain boundary, thereby enabling affection by the grain boundary to belowered. Particularly, in case of an FET device, existence of a boundaryface at a gate portion considerably deteriorates a high-frequencyproperty, a pressure-resistant property, and the like of the device.

The linear semiconductor substrate 1 or 2 is also desirable as asubstrate for a solar cell, and in that case, the P type or N typepolycrystalline silicon 4 desirably has a thickness of 0.5 μm (desirably3 μm or more) to 50 μm, and a crystal grain diameter of 10 μm (desirably50 μm or more) to several millimeters. When the linear semiconductorsubstrate of the present invention was used as a substrate of a solarcell, there was obtained a conversion efficiency of 10% to 20%.

In addition to quartz glass, usable as a linear substrate of the linearsubstrate present invention, are: high melting point materials such asceramics including multicomponent glass, sapphire, alumina, carbon,silicon carbide, and the like; metal materials such as aluminum, copper,steel, tungsten, molybdenum, alloys thereof; and the like. It isdesirable to adopt a material as a linear substrate, which has a meltingpoint equal to or higher than a melting point of a material to be usedfor deposition. In case of adoption of metal materials, reactionsthereof with semiconductor materials are caused at high temperatures,thereby requiring formation of an intermediate layer which does notreact with an oxide film nor semiconductor. Further, in case of adoptionas a substrate for a solar cell, it is desirable to adopt a material asa linear substrate which is transparent to the sunlight.

In case of quartz based glass, it is possible to adopt one doped with anetwork formation material such as boron (B), aluminum (Al), fluorine,germanium (Ge), titanium (Ti), phosphorus (P), or the like, so as toadjust a difference between thermal expansion coefficients of the quartzbased glass and a semiconductor substrate. These parent materials can beproduced by a vapor phase axial deposition (VAD) method, outside vaporphase deposition (OVD) method, or the like for producing optical fiberparent materials. It is of course possible to produce the parentmaterials, by a method other than these methods.

Further, in addition to silicon, semiconductor thin films may be madeof: compound semiconductors such as GaAs, InP, GaN, or the like; oxidesemiconductors; a so-called wide bandgap semiconductor; or the like.Conceivable as usage of linear semiconductor substrates adopting thesesemiconductors, are substrates and the like for electronic devices,IC's, light emitting devices, light receiving devices, and the like.

Second Embodiment

FIG. 2 is a cross-sectional view of linear semiconductor substratesaccording to a second embodiment. The second embodiment embraces linearsemiconductor substrates 5 and 6 comprising the linear semiconductorsubstrates 1 and 2 of the first embodiments, respectively, as well asadditional thin films 7 formed thereon, respectively. Each thin film 7is provided by depositing an oxide film, thermally-oxidized film,nitride film, or the like in a range of several nanometers to 100 nm, soas to protect the associated polycrystalline silicon 4 inside it.Examples of the thin film 7 include SiO₂, Si₃N₄, and the like. Such SiO₂comprises a thermally-oxidized film or is formed by a thermal CVDmethod.

Third Embodiment

FIG. 3 shows a cross-sectional view of linear semiconductor substratesaccording to a third embodiment. The third embodiment embraces linearsemiconductor substrates 8 and 9 each comprising a quartz glass backing3, a semiconductor thin film of polycrystalline silicon 10 deposited ona surface of the quartz glass backing 3, and another semiconductor thinfilm of polycrystalline silicon 11 formed on the semiconductor thin filmof polycrystalline silicon 10. The polycrystalline silicon 10 as thefirst semiconductor thin film is doped with boron (B), aluminum (Al), orthe like as a P type dopant, while the polycrystalline silicon 11 as thesecond semiconductor thin film is doped with phosphorus (P), bismuth(Bi), or the like as an N type dopant. The linear semiconductorsubstrates of the present invention can be each adopted as a substratefor a solar cell, and there was obtained a conversion efficiency of 12%to 15% when the polycrystalline silicon 10 thin film as the firstsemiconductor thin film had a thickness of 2 μm and the polycrystallinesilicon 11 as the second semiconductor thin film had a thickness of 0.2μm.

In the first through third embodiments, although there have beendescribed examples each including the semiconductor thin film as thethin film to be formed on the surface of the associated quartz glassbacking 3 as the linear substrate, the thin films are not limited to thesemiconductor thin films, respectively.

Mainly desirable as substrates for an organic EL, an organic EL of fibertype, and the like, are linear substrates each including the thin filmprovided by depositing a transparent electroconductive film (ITO, ZnO,SnO₂) in a range of 50 nm to several hundreds nanometers over the entirecircumference to attain a sheet resistance of 50Ω/□ or less.

Further, it is conceivable to provide a linear substrate including, asthe thin film, metal (Au, Ag, Cu, Ni, Pt, or the like) deposited in arange of 0.1 μm to 10 μm. In this case, the metal is coated afterdepositing Ti or Cr at an interface, for an improved adherence betweenthe backing and the metal. The linear substrates of the presentinvention can be each used mainly at a location where a thermalexpansion coefficient at a high temperature is to be lowered, and whereelectroconductivity is required. Alternatively, it can be used as areinforcing material, instead of usage as a substrate.

Further conceivable is a linear electroconductive substrate includingdeposited semiconductor thin films, at least one of which is anelectroconductive film, and another of which is a semiconductor thinfilm formed by coating and hardening a liquid resin. Examples of theresin to be coated include: a resist; an UV curable resin; silicone;oils such as fluorine oil, mineral oil, and the like; greases of theoils; and the like.

In case where the linear substrate for a linear solar cell has a surfaceformed with an oxide film, it is desirable to form semiconductor layersserving as the solar cell after removing the oxide film.

Fourth Embodiment

FIG. 4 shows an example of a semiconductor device and a device arrayadopting a linear semiconductor substrate according to a fourthembodiment. FIG. 4 shows a semiconductor device 21 as an exampleadopting a linear semiconductor substrate having a thermally-oxidizedfilm thereon. Included are a quartz glass 22 as a backing which is arectangular fiber (having an R of 15 μm at each corner) of 100 μm×100μm, and a p-Si film 23 having a thickness of 50 μm and a crystal graindiameter of 50 μm. Further included is a gate insulating film 24 whichis an SiO₂ film obtained by thermally oxidizing the Si thin film andwhich has a thickness of 50 nm. Furthermore, included is an inter-layerinsulating film 25 which is a combination of thermally oxidized SiO₂film and Si₃N₄ film, and which has a thickness of 100 nm. The p-Si film23 of the semiconductor device 21 is formed with an Si circuit portionhaving an area of 30×30 μm, and the device array has a length of 1,200mm when devices are arranged at intervals of predetermined pitch widths.The device array of the present invention is mainly used for a TFT fordisplay.

The linear substrates of the present invention can be each used as asubstrate of: a semiconductor device provided as a chip formed withelectronic elements such as diode, IC, LSI, or the like, opticalelements such as LD, PD, LED, or the like, solely, plurally, orcombinedly; and a module including it/them incorporated thereinto.

Examples of semiconductor devices and semiconductor device arrays otherthan the above-described ones, include those each comprising a linearsemiconductor substrate and the same or different semiconductor devicesor semiconductor device arrays formed on a plurality of surfaces of thelinear semiconductor substrate, respectively, thereby enhancing a degreeof integration of the semiconductor devices or semiconductor devicearrays.

It is possible to adopt a linear substrate having a substantiallyrectangular or substantially polygonal cross section as the linearsubstrate of the present invention, thereby providing: a semiconductorsteric device (hereinafter called “three-dimensional device”)three-dimensionally formed with devices, circuits, or wirings on aplurality of surfaces of the substrate; and a module adopting such athree-dimensional device. Here, it is possible to use one surface or twosurfaces of the three-dimensional device, as an electric contactportion(s). FIG. 5 shows examples of the semiconductor steric devices orelements. FIG. 5 shows a mount board having electrode portions connectedwith wirings of the substrate, respectively. In the device adopting sucha linear substrate, wirings can be integrated into one surface of thesubstrate, thereby enabling collective connection of the wirings byusing solder or electroconductive paste. Although such a substrate isone-dimensional, it is brought into a three-dimensional device, therebyenabling realization of an integration ratio of three or more times.

When devices are not directly formed on a linear substrate, it ispossible to use the latter as a device mount. In this case, it ispossible to integrate, on the linear substrate, materials different fromSi of the substrate, and elements such as GaAs, InP, GaN, or the like.

Further, in the three-dimensional device or the module using such athree-dimensional device, at least device portions are formed on thesame surface.

Moreover, in the three-dimensional device or the module using such athree-dimensional device, it is desirable that grain boundaries ofpolycrystalline semiconductor films formed on the linear substrate eachhave a size of 10 μm to 1,000 μm.

As another embodiment of the linear substrate of the present invention,the thin film(s) to be formed on the fiber as the linear substrate maycomprise at least one kind of metal or oxide film, or combinationthereof. Here, it is desirable that the metal(s) or oxide film(s) eachhave a specific resistance at least included in a range of Ωcm to 10⁻⁸Ωcm.

Further, as still another embodiment of the linear substrate of thepresent invention, it is possible to provide a linear substrate bydrawing out a metal through a die or by rolling the metal into a linearmaterial. When the metal is used as the linear substrate, it isconceivable to provide a linear substrate including one or more oxidefilms or metal films formed thereon.

In the linear solar cells of the present invention, it is also possibleto use, in addition to silicon, semiconductors such as binarysemiconductors like GaAs, ternary semiconductors like CuInS₂, orsemiconductors like ZnO or TiO₂ sensitized by pigment.

Fifth Embodiment

FIG. 6 shows an outline of a linear solar cell according to a fifthembodiment. FIG. 6( a) is a view showing a structure of the linear solarcell of the fifth embodiment, and FIG. 6( b) is a cross-sectional viewof the linear solar cell. It includes a quartz glass fiber 41 as alinear substrate, deposited with P type polycrystalline silicon 42thereon. The latter are each formed with a P+ type polycrystallinesilicon 43 and an N+ type polycrystalline silicon 44 at differentpositions in the longitudinal direction, respectively. This is todecrease resistances relative to electrodes 45 formed thereon,respectively. There are formed a plurality of thus constituted solarcell elements 46 in the longitudinal direction, such that the solar cellelements 46 are separated from each other and series-connected with eachother by wirings 47, respectively. The solar cell elements 46 may beconfigured to be parallel-connected and series-connected with each otherin a combined manner, depending on a design of a solar cell module. Thewirings 47 are formed at portions in the circumferential direction andsubstantially straightly aligned in the longitudinal direction.

By using the polycrystalline silicon 42 in the linear solar cell in amanner to grow the former to have a thickness of 0.5 μm or more,preferably 3 μm or more to 50 μm or less, with a crystal grain diameterof 100 μm or more, preferably 500 μm or more, the solar cell is enabledto absorb the sunlight with an excellent efficiency, while allowing aconversion efficiency of about 10% to be improved up to about 15%-18%.

When the films 42, 43, and 44 as semiconductor films are formed ofsilicon, there was obtained about 0.5V per one solar cell element as avoltage to be generated by power generation. Thus, series-connected 200pieces of solar cell elements were capable of achieving 100V. It wasfurther confirmed that, series-connecting two sets of linear solar cellsof 100V generated 200V. In a household solar cell system in the presentstate, 100V or more is used.

Sixth Embodiment

FIG. 7 shows an outline of a linear solar cell as a sixth embodimenthaving a structure different from that of the fifth embodiment. FIG. 7(a) is a view showing a structure of the linear solar cell of the sixthembodiment, and FIG. 7( b) is a cross-sectional view of the linear solarcell. It includes a linear substrate (quartz glass) 51 deposited thereonwith P+ type polycrystalline silicon 52 or W (tungsten) metal aselectrodes, respectively.

Subsequently deposited thereon are P type polycrystalline silicon 53,respectively, and further deposited thereon are N+ type polycrystallinesilicon 54, respectively, to establish diode structures. Each P+ typepolycrystalline silicon 52 and the associated N+ type polycrystallinesilicon 54 are formed with metal electrodes 55, respectively, therebyforming a solar cell element 56 having a diode structure in a thicknessdirection. Sidewalls of the solar cell elements 56 separating them fromeach other are provided with insulating films 58, respectively, formedof SiO₂, Si₃N₄, or the like, so as to avoid short circuits of wirings57. There is fabricated a plurality of thus constituted solar cellelements 56 in the direction of the linear substrate, and the elementsare connected with each other by the wirings 57, respectively, therebyestablishing the linear solar cell.

Also in the linear solar cell of the sixth embodiment and similarly tothe linear solar cell of the fifth embodiment, there were fabricatedlinear solar cells each having a thickness of 6 μm and a length of 1 m,by using linear substrates 51 having diameters of 0.07, 0.1, and 0.2 mm,respectively. One thread of solar cell was formed with 200 pieces ofsolar cell elements 56, and 100 threads of such solar cells wereparallel-connected to obtain a voltage of about 100V. When the linearsubstrate 51 had a diameter of 0.07 mm, there was averagedly obtainedabout 0.01 W with a film thickness of 2 μm, and there was similarly andaveragedly obtained about 0.014 W with a film thickness of 6 μm. Whenthe linear substrate 51 had a diameter of 0.1 mm, there was averagedlyobtained about 0.015 W with a film thickness of 2 μm, and there wassimilarly obtained 0.02 W with a film thickness of 6 μm. Further, whenthe linear substrate 51 had a diameter of 0.2 mm, there was averagedlyobtained about 0.03 W with a film thickness of 2 μm, and there wassimilarly obtained 0.04 W with a film thickness of 6 μm. Note that theabove results were confirmed by a solar cell system having aconfiguration that wirings were laid at a reverse side of a lightreceiving face while adopting an aluminum mirror plate as a reflectiveplate.

Although there have been described linear solar cells each having a PNjunction or PIN junction in the thickness direction of the associatedthin films, it is also possible to form a linear solar cell having an NPjunction or NIP junction.

In the cross section of the linear solar cell of the fifth embodiment orthe linear solar cell of the sixth embodiment, there has been adopted aquartz glass having a circular cross section as the quartz glass fiber41 or 51. In case of adoption of such a transparent linear substratehaving a circular cross section, incident light is absorbed by thesemiconductor films at the surface, and part of the light is transmittedthrough the semiconductor films since they are thin. The transmittedlight is partially reflected by an interface between the transparentlinear substrate and the applicable semiconductor film, is partiallytransmitted through the linear substrate, and is then absorbed by thesame semiconductor film. In this way, reflection and absorption arerepeated at the interface between the linear substrate and theapplicable semiconductor film, thereby obtaining such a remarkable meritof the linear substrate that the light is effectively absorbedirrespectively of the small thicknesses of the semiconductor films. Incase of a conventional solar cell adopting a two-dimensional substrate,there was required a film thickness of 20 μm.

As the cross-sectional shape of the linear solar cell, it is conceivableto adopt a polygonal shape, rectangular shape, a combined shape of arcand rectangle, and the like, in addition to the circular shapes shown inFIG. 6 and FIG. 7.

FIG. 8 shows an example of a solar cell module. It has a structure tosupport a solar cell array comprising juxtaposed linear solar cells 61by a reflective plate 62 made of aluminum. The linear solar cells 61 areeach formed with an anti-reflection film 63 made of SiO₂ or Si₃N₄ film.Such a configuration allowed a power generation efficiency of 12-15% tobe improved up to 17-20%. Further, taking account of arrangement andhandling of the linear solar cells 61, it is also possible for thelinear solar cells 61 to each have a polygonal cross section shape suchas a rectangular shape or the like, or have a shape including a straightside formed as a part thereof.

Seventh Embodiment

FIG. 9 shows an outline of a solar cell system adopting a linearsubstrate according to a seventh embodiment. FIG. 9( a) shows an exampleof a solar cell module 71 constituted to include linear solar cells 72juxtaposed on a reflective plate 73. Further, FIG. 9( b) is a viewshowing a configuration of the solar cell system when the solar cellmodule 71 is used as an AC electric-power source. The solar cell module71 is configured to be connected with a discharge/charge controller 74and an inverter 75, thereby providing a power source to a load 77 ofelectric equipment or the like. Further, the module is also connectedwith a battery 76 for storing electric power generated in the daytime.

The solar cell module 71 is to desirably have a thickness between 0.04mm inclusive and 10 mm inclusive except for the reflective plate 73.

According to the solar power generation system adopting the linearsubstrates of the present invention, it is possible to produce anextremely light-weighted solar cell module. For example, devicesrequired for a solar cell of 1 m² have a weight of about 9 kg in case ofadoption of two-dimensional glass substrates (4 mm thick), and a weightof about 700 g in case of the linear substrates of the presentinvention, which means light-weighting down to 1/10 or less. This alsoallows a solar cell module to be remarkably light-weighted, therebyobtaining a remarkable economical effect to allow for decrease oftransportation cost, installation cost, construction cost, and the likeby 20% to 30%.

The linear solar cell array of the present invention is packaged into astand provided with terminals to be connected to wirings, respectively.

Since the solar power generation system adopting the linear substratesof the present invention can be light-weighted and is excellent inflexibility simultaneously therewith, it is exemplarily possible toconstitute a solar cell 78 in a bamboo blind shape as shown in FIG. 10,a foldable solar cell module (not shown), and the like. In FIG. 10,there are omitted details of wirings for connecting linear solar cells79 with each other, and the like. The solar cell 78 of the presentinvention can be produced by interposing, the duly arranged and wiredlinear solar cells 79, between transparent sheets (such as PET, acrylicresin, vinyl chloride resin, polycarbonate resin, or the like), and bylaminating the latter to the former by adhesive or heat sealing. As anapplied example, it is conceivable to adopt the solar cell as a sunshade sheet in a vehicular compartment, for example, to thereby rotate asmall fan by power generation by the solar cell in a state wherepassengers are absent, or to thereby cool the interior of the vehicle byconnecting Peltier elements to the solar cell. It is also possible touse the solar cell as a blind or bamboo blind in a room to utilize agenerated electric power, to thereby drive an electric fan, or tothereby charge a power source of a personal computer or a cellular phoneitself, for example.

There will be explained fabricating methods of the linear substrates ofthe present invention, based on the drawings.

Eighth Embodiment

As an eighth embodiment, there will be explained a fabricating method ofthe linear substrate of the present invention, with reference to FIG.11. The present invention utilizes a fiber-drawing technique which is afabricating technique of an optical fiber for realizing a higherthroughput. FIG. 11 shows a first heater 102 for heating and melting apreform (quartz glass parent material) 101, and other heaters 103through 105 for exemplarily heating a raw material gas, and adjustingtemperatures of ambiences. Ambiences in the installed locations of theheaters 102 through 105 are separated from that in the location of thepreform 101 by a reaction furnace core pipe 106. Typically used as thereaction furnace core pipe 106 is carbon. Further, at a low temperaturelocation, it is possible to use a reaction furnace core pipe comprising:quartz; SiC; or carbon or SiC having SiC coating (deposited by thermalCVD) applied thereto.

To keep the pressure within the reaction furnace core pipe 106 at theatmospheric pressure or higher, or to establish a pressurized ambienceif required, there is supplied an inert gas such as Ar, He, or the like,or a mixed gas thereof into the reaction furnace core pipe 106. Supplyof the inert gas has an effect to avoid entrance of atmospheric air intothe reaction furnace core pipe 106 and to simultaneously prevent theharmful raw material gas, reaction gas, and the like from flowing out ofthe reaction furnace core pipe. Note that, in case of deposition of acompound semiconductor, there is supplied: a vapor of a raw materialhaving a higher vapor pressure; a gas including the raw materialcomponent; or a mixed gas of the same and an inert gas such as Ar, He,or the like.

The inert gas such as Ar, He, or the like supplied into the reactionfurnace core pipe 106 is mainly exhausted through an exhaust port 107 atan upper portion of the reaction furnace core pipe, while the rawmaterial gas or the gas generated by reaction is exhausted through anexhaust port 108 at a lower portion of the reaction furnace core pipe.Preferably, it is desirable to provide shield means, within the reactionfurnace core pipe 106, for separating the ambient gases and the rawmaterial gas from each other, thereby preventing them from being mixedwith each other. Provided at an exit of the reaction furnace core pipe106 is a shutter (not shown) for narrowing the exit.

In FIG. 11, the second heater 103 is one provided for reaction, with aconfiguration that the raw material gas is supplied when the temperatureof a quartz glass fiber as a linear substrate is in a range of 1,430° C.to 1,600° C. which is higher than the melting point of 1,412° C. ofsilicon. It is thus considered that deposited silicon is present in aliquid state on the surface of the fiber. Although the conventionaldeposition method achieves deposition in vacuum by using PCVD orsputtering, the linear substrate fabricating method of the presentinvention is remarkably different therefrom in that deposition isachieved in an ordinary pressure state or pressurized state by thermalCVD (or CVD using electromagnetic induction or light). This enables adeposition rate to be drastically improved.

In FIG. 11, the two heaters 104 and 105 at a lower section are providedto grow crystal grain diameters of silicon formed on the quartz glassfiber as the linear substrate. Cooling at an appropriate temperaturegradient allows the crystal grain diameters to be grown as the moltensilicon is cooled. By virtue of the thermal CVD, it is possible to allowgrain boundary sizes to be grown to about 20 to 100 μm. Controlling thetemperature gradient commensurately with a fiber-drawing speed of thequartz glass fiber, a deposition thickness of the polycrystallinesilicon, and the like, enables to appropriately deal with fluctuation ofthe fiber-drawing speed, fluctuation of deposition thickness, and thelike. It is also possible to change a deposition rate in terms of aposition in a longitudinal direction. Note that the process for growingcrystal grain diameters of silicon comprises two or more steps includinga nucleus generation step, and a crystal growth step. The third heater104 and fourth heater 105 shown in FIG. 11 correspond to the nucleusgeneration step and crystal growth step, respectively. Since the nucleusgeneration has a temperature dependency, it is desirable to set aheating temperature within a range of 400° C. to 1,000° C. in thenucleus generation step. Further, more higher temperatures are desirablefor growing crystals, and it is desirable that the heating temperatureis set within a range of 1,000° C. to 1,500° C. in the crystal growthstep.

The above described linear substrate fabricating method of thisembodiment is different from a fiber-drawing method for an opticalfiber, in that: the heating furnace has its upper portion of ahermetically sealed type; the raw material gas (raw material gas ofSiCl₄, SiHCl₃, or the like for silicon, and further a doping gas PCl₃,BCl₃, or the like for solar cell) is supplied by a vapor pressurethereof, by bubbling it by Ar, He gas, or the like, or by directlyheating the raw material, in the heating furnace; deposition is achievedin an ordinary pressure state or pressurized state; and there isprovided a temperature distribution in the longitudinal direction offiber drawing, by the plurality of heaters.

Although the reaction furnace core pipe of the eighth embodiment isprovided with the four heaters, it is also possible to attain all thefunctions by a single heater, by changing a heater design.

In FIG. 11, the fiber exiting the fiber-drawing furnace is cooled by acooling apparatus 109, is coated with a resin, a resist, and the like ata resist coating portion 110 to be used in a step of device fabrication,followed by hardening at a resist hardening portion 111. At the coolingapparatus 109, cooling is conducted by using He gas. The reason why theresin, resist, and the like are coated at the resist coating portion110, is to protect the deposited film on the quartz glass fiber.Desirably, to be adopted as the resin is an ultraviolet-curable resin oran electron beam curable resin. The deposited film suitably has athickness in a range of 0.5 μm to 30 μm, and preferably 1 μm to 10 μm.The linear substrate coated with the resin, resist, and the like isdrawn out by a capstan 112 and wound onto a double spooler 113. Herein,the double spooler 113 is a winder capable of conducting a changeoverfrom a fully wound bobbin during its winding, to the other empty bobbinwithout lowering a fiber-drawing speed. Bobbins each have a windinglength of 50 km to 200 km, so that fabricating of a linear semiconductorsubstrate of 1,000 km requires 5 to 20 pieces of bobbins. Fiber-drawingspeeds of 5 m/s to 30 m/s are possible.

The linear semiconductor substrate of the present invention has across-sectional shape which can be set by previously working the preform101 into a desired shape. For example, the cross-sectional shape of thequartz glass backing 3 of FIG. 1 is rectangular having R's at corners,respectively, and this can be realized by setting the cross-sectionalshape of the preform 101 into a similar rectangle having R's at corners,respectively. Only, the R portions are likely to be enlarged, due toslightly rounded corners by fiber-drawing. Nonetheless, it is possibleto restrict the change in cross-sectional shape, by setting thetemperature upon fiber-drawing at 2,000° C. or lower. Examples ofmethods for lowering the temperature upon fiber-drawing to therebyattain a low temperature at about 1,800° C., include prolonging theheater 102 for fiber-drawing in a fiber-drawing direction, setting aplurality of heaters 102 for fiber-drawing, controlling the temperatureof the second heater 103 for reaction at a higher level, or the like.

As a method for controlling a cross-sectional shape of the linearsemiconductor substrate of the present invention, it is possible toadopt a fiber-drawing technique for a typical optical fiber. Namely, thequartz glass preform 101 worked into a desired shape is heated andmelted by the heater 102 for fiber-drawing, and then spun; the shape ofthe fiber withdrawn by the capstan 112 is measured by an outer diametermeasuring equipment or a shape measuring equipment; the fiber iswithdrawn by the capstan 112, while controlling the withdrawing speed ofthe fiber, or the feeding speed of the preform 101, or both, and thefiber is wound up by the winder 113, so that the shape of the fiber ismade constant; thereby enabling the cross-sectional shape of the linearsemiconductor substrate to be controlled. When the linear semiconductorsubstrate has a circular cross section, it is possible to restrict thefluctuation of its outer diameter to ±1 μm or less.

Although the fiber-drawing furnace and the reaction furnace areintegrated with each other in the linear substrate fabricating method ofthe present invention shown in FIG. 11, these may be separated from eachother. Shown in FIG. 12 is an embodiment including a fiber-drawingfurnace and a reaction furnace separated from each other. Thisembodiment includes the fiber-drawing furnace 121 and the reactionfurnace 122 separated from each other. It is required to ensureairtightness between the fiber-drawing furnace 121 and the reactionfurnace 122 lest the atmospheric air or the like moves into theinteriors of them, and this embodiment includes a coupling tube 123provided between the fiber-drawing furnace 121 and reaction furnace 122to thereby couple them to each other. Alternatively, it is desirablethat the furnaces contain ambiences such as inert gas or the like,respectively, to keep pressures within the furnaces higher than theatmospheric pressure, thereby establishing a structure which theatmospheric air never enters.

Instead of growing crystal grain diameters by the two heaters 104 and105 at the lower section shown in FIG. 11, it is also possible toprovide a stage for growing by supplying an energy such as light, heat,electromagnetic induction, or the like, or to provide a stage forirradiating laser light for recrystallization. Adopting laser anneal tothereby irradiate a laser beam to a linear substrate promotes crystalgrowth (one-dimensional crystal growth) substantially selectively in ascanning direction of the laser beam, thereby enabling a grain boundaryto be enlarged.

It is further possible to conduct a procedure to enlarge the crystalgrain of the formed semiconductor thin film, during the fiber-drawingstep or during another step, to thereby bring the grain diameter of thecrystal grain to φ40 μm or more.

Moreover, it is possible to anneal the deposited film, by prolonging thereaction furnace or by adding a furnace for annealing. The temperaturetherefor is preferably at or lower than a distortion point of the glassas the parent material. Such a temperature is about 1,100° C. in case ofquartz glass, and is about 600° C. to 1,000° C. depending on a dopantconcentration in case of a quartz based glass containing a dopant.

Further, it is possible to cause the semiconductor thin film to beformed of silicon, by reducing a surface of the fiber which is spun fromthe preform 101.

Ninth Embodiment

There will be explained a linear substrate fabricating method of thepresent invention based on FIG. 13, as a ninth embodiment. Thefabricating method of the present invention shown in FIG. 13 is relatedto one for the linear semiconductor substrate explained with respect toFIG. 2 and formed with the additional thin film 7 such as an oxide film.The linear substrate fabricating method of this embodiment issubstantially the same as the fabricating method of the eighthembodiment explained with respect to FIG. 11. However, in FIG. 13, thereare supplied a silicon raw material such as SiCl₄ from a supply port131, and oxygen O₂ from a supply port 132, so as to form the additionalthin film 7 on the polycrystalline silicon 4 as the first thin film. Inthis way, there is formed a thermally-oxidized film on thepolycrystalline silicon 4 as the first thin film, during passage throughthe heater 105.

As an example of the linear semiconductor substrate produced by thefabricating method of the present invention shown in FIG. 13, the quartzglass preform 101 in a rectangular cross section of 40 cm×40 cm wasmelted and spun by the first heater 102, thereby producing a rectangularfiber (R's at corners are each 10 μm) of 80 μm×80 μm. The drawn fiberwas deposited, on its surface, with an Si film having a thickness of 55nm at the second heater portion 103, and there was deposited an SiO₂film having a thickness of 50 nm at the fourth heater portion 105 whileannealing crystal grains to thereby grow them at the third heaterportion 104. Further, coated onto the fiber at the resist coatingportion 110 was a resist film which was thermally hardened at thethermal hardening portion 111, and thereafter the fiber was withdrawn bythe capstan 112 and wound up by the winder 113. The polycrystallinesilicon thin film of the obtained linear semiconductor substrate had acrystal grain diameter of 55 μm and an electron mobility of 105 cm²/Vs.Note that it is possible to deposit an Si₃N₄ film at the fourth heater105, instead of deposition of an SiO₂ film.

In case of forming a thermally-oxidized film at a smaller thickness, itis possible to form such a thermally-oxidized film, by supplying oxygenor steam to thereby react it with the polycrystalline silicon 4 formedon the quartz glass backing 3.

Also in case of forming a semiconductor thin film by a method other thanthe thermal CVD, there is provided a heating furnace for forming anoxide film in case of formation of the oxide film on the semiconductorfilm.

It is further possible to form a film of silicon nitride (Si₃N₄),instead of the thermally-oxidized film, or on the thermally-oxidizedfilm. In case of formation of a silicon nitride film, there are supplieda raw material gas and a nitrogen or ammonia gas into the same furnaceas the fiber-drawing furnace during fiber-drawing or into anotherfurnace to thereby form an oxide film of several nanometers to severalhundreds nanometers, similarly to the case of forming thethermally-oxidized film.

Tenth Embodiment

There will be explained a linear semiconductor substrate fabricatingmethod for forming two layers of thin films comprising a P typepolycrystalline silicon and an N type polycrystalline silicon to bematured into a solar cell, based on a tenth embodiment shown in FIG. 14.This embodiment is substantially the same in constitution as the ninthembodiment shown in FIG. 13, and is different therefrom in that thisembodiment supplies, from a supply port 133, a boron (B) or aluminum(Al) raw material or the like serving as a P type dopant in addition toa silicon raw material (SiCl₄, SiCl₃H, or the like) so as to firstlyform a P type polycrystalline silicon. This embodiment is furtherdifferent in that it supplies, from the supply port 131, a phosphorus(P) or bismuth (Bi) raw material or the like serving as an N type dopantin addition to the silicon raw material so as to form an N typepolycrystalline silicon. Note that the deposited semiconductor has acarrier concentration which can be controlled by a concentration of thedopant to be supplied.

In FIG. 13 and FIG. 14, when the preform 101 is provided in a mannerthat a porous parent material doped with germanium (Ge) is treated in areducing atmosphere such as carbon, Si, CO (carbon monoxide), SiC or thelike to thereby form amorphous silicon or polycrystalline silicon on thesurface of the parent material, or when the preform 101 is provided bydepositing silicon on a quartz parent material, deposition of additionalsilicon onto the matured fiber formed with the original silicon at itssurface improves adherence of the additional silicon with the quartzglass. This allowed a silicon film to be easily formed at a filmthickness of 5 μm. Further, production was enabled at a fiber-drawingspeed of 30 m/s or more. Conducting growth of deposited semiconductorgrains enabled realization of a linear substrate for a solar cell havinga higher conversion efficiency.

According to the fiber-drawing methods shown in FIG. 13 and FIG. 14, itis possible to form a part or whole of an internal electrode and ofsemiconductor layers to be matured into a solar cell, between theapplicable furnace and the associated capstan 112. It is also possibleto provide a step for forming an intermediate layer between theapplicable fiber and the associated internal electrode.

Eleventh Embodiment

There will be explained another linear semiconductor substratefabricating method of the present invention, based on an eleventhembodiment shown in FIG. 15. This fabricating method of the presentinvention is configured to: fiber-draw a preform 101 through the firstheater 102; cool the drawn fiber by the cooling apparatus 109; coat,onto the fiber, a semiconductor particle containing liquid at a coatingapparatus 141; and dry, melt, solidify, or solid-phase sinter it at amelting/solidifying portion 142; thereby forming a semiconductor thinfilm. In this fabricating method of the present invention, no rawmaterial gas for a semiconductor thin film is supplied into the reactionfurnace core pipe 106.

Further, it is also possible to form a semiconductor film, by melting adesired semiconductor and by directly coating it onto a fiber as alinear substrate.

As an example utilizing the fabricating method of this embodiment shownin FIG. 15, the quartz glass preform 101 in a rectangular cross sectionof 40 cm×40 cm was melted by the first heater 102, and spun into arectangular fiber (R's at corners are each 15 μm) of 150 μm×150 μm. Thedrawn fiber was cooled by the cooling apparatus 109; the fiber was thencoated with a paste-like liquid including silicon particulates suspendedtherein, by a coating die at the coating apparatus 141; and the coatedliquid was heated and fired to 1,500° C. and cooled, at themelting/solidifying portion 142. Further, the fiber was coated with aresist film at the resist coating portion 110 followed by thermalhardening at the thermal hardening portion 111, and then wound up by thewinder 113. The linear semiconductor substrate produced by theproduction method of the present invention included a polycrystallinesilicon film having a thickness of 60 nm, a crystal grain diameter of 50μm and an electron mobility of 100 cm²/Vs.

Concerning a linear substrate comprising a quartz glass backing as alinear substrate having a surface formed with a transparentelectroconductive film, the fabricating method of a linear ITO substrateincluding the transparent electroconductive film formed of ITO issubstantially the same as the embodiment explained in FIG. 11 or 13, andis different therefrom in that: the raw material for the thin film isdifferent; and there is unrequired a process for growing a crystal suchas in case of a semiconductor, thereby requiring only two heating zonesat a location for heating and melting a preform, and another locationfor reacting a raw material of thin film with the preform.

Further, in case of the fabricating method shown in FIG. 15 adapted todeposit ITO by sintering it after coating it onto a fiber: no rawmaterial gas is to be flowed into the reaction furnace core pipe 106;the melted and spun fiber is cooled by the cooling apparatus 109 andthen coated with a liquid raw material by the coating apparatus 141; itis heated and fired at the melting/solidifying portion 142; it is coatedwith a protective film; and it is then wound up by the winder 113. Forimproved adherence with the backing, it is desirable to coat the rawmaterial after coating a base resin.

There will be explained a fabricating method of a two-dimensional orcurve surfaced module adopting the linear substrate of the presentinvention, based on FIG. 16. The module fabricating method of thepresent invention includes operations which can be roughly classifiedinto four processes. The first one comprises a linear substratefabricating process 151 for producing a linear substrate of the presentinvention, the second one comprises a segmenting process 152 forintegrating linear substrates with each other into segments or arrays,the third one comprises a device fabrication process 153 for formingdevices, and the fourth one is a modularizing process 154 for arrangingthem into a two-dimensional flat plane or curved plane.

In FIG. 16, linear substrates are segmented and integrated at thesegmenting process 152 into a roller substrate 155 or a flat substrate(not shown) to thereby allow compactization, thereby allowing anapparatus of the device fabrication process 153 to be downsized. Thisdrastically decreases an equipment cost for the device fabricationprocess 153, and allows a throughput to be enhanced to several tenstimes, several hundreds times, or even to several thousands times.Further, it is unnecessary to apply an excessive tension to the linearsubstrate, and the process can be implemented in a non-contact manner.

The fabricating method of the two-dimensional or curve surfaced moduleutilizing the linear substrate of the present invention as explainedbased on FIG. 16, can be directly applied to a case where the linearsubstrate is a linear solar cell.

There will be explained a two-dimensional or curved plane modulefabricating method which is different from the fabricating methodexplained in FIG. 16, with reference to FIG. 17. In FIG. 17, thefabricating method is shown for a solar cell module, for example. Thisfabricating method of the present invention can be classified into threeprocesses. The first one comprises a linear substrate/backingfabricating process 161 for producing a linear substrate or linearsubstrate, the second one comprises a device fabrication process 162 forforming solar cell elements onto the wound up linear material, and thefinal third one comprises a modularizing process 163 for arranging theminto a two-dimensional flat plane or curved plane.

Further, the device fabrication process 162 as the second processcomprises a coating (protective film) removal step 165, a semiconductordeposition step 166, a doping step 167, an element separation step 168,an electrode formation step 169, and a cutting step 170. Depending ondesigns of the fabricating steps, it is possible to supply the linearsubstrate or linear backing by a bobbin at each process, and to wind upit onto another bobbin at the end of the processes. In this case, it isdesirable to wind up the linear substrate onto the bobbin after forminga protective film on the substrate, so as not to damage the processedfilms thereon. Further, it is desirable to simultaneously processseveral threads to several tens threads of linear substrates, for animproved productivity.

Moreover, in the device fabrication process 153 in FIG. 16 or the devicefabrication process 162 in FIG. 17, although it is possible to treat thesubstrate(s) in a vacuum process by conducting differential evacuation,it is desirable to adopt an atmospheric process in consideration ofproductivity and maintenance ability. For example, it is conceivable toadopt processes of: coating removal, semiconductor deposition, etching,electrode formation, and the like by atmospheric plasma; removal ofprotective film by wet etching; wiring by ink jet, dispenser, orprinting technique; etching by laser; and the like.

As an example of the segmenting process 152 shown in FIG. 16, it isconceivable to use a process constituted of: means for drawing out thecoated linear semiconductor substrate wound on a bobbin, at a constanttension; means for fixing the linear semiconductor substrate onto anintegrated-substrate holder; integrated-substrate holder moving meansfor moving the integrated-substrate holder to thereby arrange the linearsemiconductor substrate at intervals of predetermined spacings; andmeans for cutting the linear semiconductor substrate.

As another fabricating method of a linear solar cell of the presentinvention, there is a method which adopts a linear substrate comprisinga fiber-shaped glass backing formed with an internal electrode, and/oran N type or P type semiconductor layer to be included in a solar cell,and which method conducts, at least procedures: to deposit asemiconductor having a polarity opposite to that of the linearsubstrate, or to form a semiconductor having a relatively highresistance and deposit or dope a semiconductor having a polarityopposite to that of the linear substrate, thereby forming elements; toseparate the elements from each other; and to form electrodes betweenthe elements, respectively.

It is further possible to implement a process treatment for a solar cellby using a linear substrate formed with a part or whole of electrodes,semiconductor films, and the like constituting solar cell elements,respectively, to thereby fabricate a linear solar cell.

In the linear substrate fabricating methods of the present invention, itis possible to use a high temperature process (such as thermal CVDmethod, high temperature plasma method, or the like) by utilizing afiber-drawing technique for an optical fiber. This enables formation ofdeposited films at a higher speed as compared with a conventional vacuumprocess, and the steps thereafter can also be conducted at a higherspeed, thereby enabling production of linear semiconductor substrates ata lower cost.

By adopting the backing made of quartz glass, it becomes possible todrastically decrease a film thickness of a semiconductor portion ascompared with a semiconductor wafer substrate. Although the linearsemiconductor substrates of the present invention each adopts expensivequartz glass, the usage amount of quartz glass can be remarkablydecreased by virtue of the nature of a linear substrate, while enablingobtainment of quartz glass at a relatively low cost by utilizing asynthesizing technique for an optical fiber. This enables the cost ofthe backing to be decreased down to the same or lower level as or thanthat of a conventional multicomponent glass substrate.

Although the linear substrate fabricating method of the presentinvention is required to include production facilities located in a tallbuilding due to the usage of the fiber-drawing technique for an opticalfiber, the producing apparatus itself is remarkably inexpensive ascompared with a semiconductor producing apparatus or agrinding/polishing/producing apparatus of a glass substrate for liquidcrystal or the like, thereby enabling an equipment investment to berestricted. Further, the drawn fiber has a clean surface, and roughnesswithin a size of a device is as small as several nanometers to severaltens nanometers, thereby eliminating necessity of cleaning and polishingbefore deposition, which also becomes a factor of a decreasedfabricating cost.

In any one of the manufacturing methods of the present invention, it ispossible to realize deposition at a high speed which is 10 times to 100times faster than a speed for deposition by a vacuum method, and toproduce a linear semiconductor substrate at a high throughput (highspeed at 20 m/s or more) and a decreased cost. For example, in case of asubstrate of 1 m², there is weighed about 9 kg for a two-dimensionalsubstrate and there is weighed 700 g for an array of linear substrates,thereby enabling a usage amount of backings to be decreased down to 1/10or less. Further, according to the method of the present invention, eachsemiconductor film to be formed on a linear substrate is never contactedwith any solid matter until the semiconductor film is deposited to arequired thickness, and then the substrate is coated with a protectivefilm followed by withdrawal by the capstan and thereafter wound up bythe winder. Thus, there is no risk to damage the deposited semiconductorfilm, thereby enabling production thereof at a higher speed.

The fabricating method of the present invention is configured to conductalso the process for growing semiconductor grains in the course of thefiber-drawing process in an on-line manner. This process can be realizedby establishing a suitable temperature distribution in a fiber-drawingdirection. The method of the present invention is to apply an SOI (Si OnInsulator) technique established in case of TFT (thin film transistor)of a two-dimensional substrate to a linear substrate. Further, in caseof a conventional two-dimensional substrate, polycrystalline silicondeposited at a low temperature was locally heated by laser at a separateprocess to thereby melt the polycrystalline silicon in a lineardirection, followed by cooling to grow a crystal grain. By adjusting anoperation speed of the laser, the cooling speed of the molten silicon iscontrolled. The linear semiconductor substrates are each sufficientlysmall in substrate width, and in a depth or radius direction, therebyenabling obtainment of a substantially uniform temperature distribution.Further, controlling the temperature distribution in the longitudinaldirection of the fiber by heating means such as a heating furnace,allows for precise temperature control. Moreover, adopted as the backingis a material having a heat resistance higher than a melting point of amaterial to be deposited to thereby allow for deposition at atemperature higher than the melting point of the material to bedeposited, thereby enabling deposition at a higher speed.

The present invention adopts quartz glass as a backing for semiconductor(SOI), thereby achieving a sufficient heat resistance of the backingagainst a melting point of a material to be deposited. This allowsadoption of a high-temperature process (chemical reaction athigh-temperature) also for an oxide (such as TiO₂ or the like)semiconductor and carbide (such as SiC or the like), thereby enablingobtainment of a film quality better than that obtained by a conventionalscheme for adopting a vacuum process. Meanwhile, in case of a compoundsemiconductor, it is likely that a stoichiometric composition is notobtained due to a difference of vapor pressure, and defects areincreased. In this case, it is effective to raise a pressure of anambience, by a raw material gas mixed with: a gas including a highlyvolatile component; an inert gas; or the like. This is applicable,although the apparatus may be complicated.

In case of adoption of silicon tetrachloride (SiCl₄) in FIG. 11 or FIG.12, progress of the reaction leads to production of chlorine (Cl₂) orhydrogen chloride (HCl) to thereby cause an etching reaction, such thatetching finally becomes dominant over deposition. To avoid it, there issupplied a raw material gas in a manner to arrange holes for injectingthe raw material gas at certain intervals in a flowing direction thereof(FIGS. 18, 19, and 20), thereby prolonging a zone of depositionalcondition (i.e., a zone where the raw material concentration can be madesufficiently higher than that of the above-mentioned reaction product,thereby allowing deposition). Further, slightly prolonging the intervalslead to exposure to an etching ambience to thereby enable restriction ofgrowth in an orientation apt to be etched. This enables an intendedcontrol to a certain extent. In the present invention, there areprovided supply ports and exhaust ports at intervals of 50 mm to 300 mm.The intervals are adjusted depending on a fiber-drawing speed, atemperature of the reaction furnace, or a fiber temperature, so as toattain the fastest deposition rate by the provided supply ports.

INDUSTRIAL APPLICABILITY

At least one layer of intended thin film 4 is formed on a linearsubstrate 3 having a length ten or more times greater than a width,thickness, or diameter of the backing itself so as to form a linearsemiconductor substrate, thereby allowing the linear semiconductorsubstrate to be readily applied to a device, device array, module,display, solar cell, and solar cell module, utilizing the linearsemiconductor substrate.

1. A linear substrate for semiconductor devices, comprising: a linearcore made of an electrical insulator and having a micro-scaled crosssection; and a semiconductor film formed on an outer surface of thelinear core, wherein said semiconductor film has a melting point lowerthan a melting point of said linear core, and said semiconductor filmhas a grain boundary composition having a grain size of at least tenmicrometers.
 2. The linear substrate according to claim 1, wherein saidlinear core is made of an optical fiber.
 3. The linear substrateaccording to claim 2, wherein said optical fiber is made of quartzglass.
 4. The linear substrate according to claim 1, wherein said linearcore is made of a transparent material.
 5. The linear substrateaccording to claim 1, further comprising: an additional semiconductorfilm formed on said semiconductor film.
 6. The linear substrateaccording to claim 1, wherein the micro-scaled cross section of saidlinear core is circular shaped.
 7. The linear substrate according toclaim 1, wherein the micro-scaled cross section of said linear core ispolygonal shaped.
 8. The linear substrate according to claim 1, whereinsaid semiconductor film is made of a polycrystalline silicon.
 9. Thelinear substrate according to claim 1, further comprising: semiconductordevices formed on said semiconductor film.
 10. The linear substrateaccording to claim 1, further comprising: a film formed on said linearsubstrate, said film including: an electroconductive film; and a resinfilm in a form of either a coated liquid resin or a coated and hardenedliquid resin.
 11. The linear substrate according to claim 10, whereinsaid electroconductive film is substantially transparent in a visiblerange, and comprises indium tin oxide (ITO), tin oxide (SnO₂) or zincoxide (ZnO).
 12. The linear substrate according to claim 10, whereinsaid resin film is formed with: a resist; a UV curable resin; silicone;oils such as fluorine oil or mineral oil; or greases of the oils. 13.The linear substrate according to claim 1, further comprising: a metaland/or oxide film formed on said linear substrate.
 14. The linearsubstrate according to claim 1, further comprising: a protective filmremovably formed on said linear substrate.
 15. The linear substrateaccording to claim 1, wherein said semiconductor film is an outermostlayer of said linear substrate.